1. Field of the Invention
Embodiments of the invention generally relate to processing chambers having a restricting ring for improving flow uniformity.
2. Background of the Related Art
Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density that demand increasingly precise fabrication techniques and processes. One fabrication process frequently used is chemical vapor deposition (CVD).
Chemical vapor deposition is generally employed to deposit a thin film on a substrate or semiconductor wafer. Chemical vapor deposition is generally accomplished by introducing a precursor gas into a vacuum chamber. The precursor gas is typically directed through a showerhead or other inlet situated near the top of the chamber. The precursor gas reacts to form a layer of material on the surface of the substrate that is positioned on a heated substrate support.
The uniformity of the material deposited during chemical vapor deposition processes is dependent on many factors, including the uniformity of the flow of precursor gas across the diameter of the substrate. As many process chambers have a vacuum port formed through the sidewalls of the vacuum chamber, the pumping conductance is generally highest at the edges of the substrate closest to the vacuum port. This results in increased flows over this area while less precursor, and hence, less deposited material, is present over the other regions of the substrate.
One evolving CVD technique is known as atomic layer deposition. ALD is a specialized chemical vapor deposition technique that deposits a film one molecule thick on the substrate during each deposition cycle. This is typically accomplished by providing a gas flow sequence of discrete, small volumes of reactant and precursor gases separated by a purge. As these volumes of gas flow are small as compared to conventional CVD processes, the uniformity of gas delivery to the substrate surface is of even greater importance than in conventional CVD processing chambers.
Therefore, is a need for a processing chamber having improved gas flow uniformity.
One aspect of the present invention generally provides a processing chamber having a flow-restricting ring for enhancing flow uniformity over substrates processed within the processing chamber. In one embodiment, a processing chamber includes a chamber body, a lid assembly, a substrate support and a flow-restricting ring. The chamber body has sidewalls and a bottom. The lid assembly is disposed on the sidewalls and encloses an interior volume of the chamber body. The substrate support is disposed in the interior volume of the chamber body and is adjustable in elevation between the lid assembly and the bottom of the chamber body. The flow-restricting ring has an outer edge disposed proximate the sidewalls of the chamber body and an inner edge disposed proximate the substrate support when the substrate support is disposed in an elevated position. The inner edge of the ring and the substrate support are disposed in a spaced-apart relation defining an annular flow control orifice. The flow control orifice enhances flow uniformity across a substrate positioned on the substrate support during processing.
In another embodiment, a processing chamber includes a chamber body, a lid assembly, a substrate support assembly, a ring and a seal. The chamber body includes sidewalls and a bottom. The lid assembly is disposed on the sidewalls and encloses an interior volume of the chamber body. The substrate support assembly is disposed in the interior volume of the chamber body and is adjustable in elevation between the lid assembly and the bottom of the chamber body. The ring is disposed between the lid assembly and the sidewalls. The ring has an outer edge disposed proximate the sidewalls and inner edge proximate the substrate support assembly. The ring has a plurality of holes formed therethrough. The substrate support may be elevated to a position to contact the seal, thus prevetning flow between the substrate support assembly and the ring.
In another aspect, a method for controlling flow in the processing chamber is provided. In one embodiment, the method includes the steps of elevating the substrate support assembly to a position proximate a ring, wherein the ring and substrate support define an annular orifice radially outward of the substrate support, flowing gas into a processing region defined above the substrate support and the ring, flowing gas from the processing region through the annular orifice to a pumping plenum and exhausting gas from the pumping plenum through an exhaust port disposed in the processing chamber.
In another embodiment, a method for controlling the flow of the processing chamber includes the steps of elevating a support assembly to sealingly contact a ring disposed in the processing chamber, flowing gas into a processing region defined above the substrate support assembly and the ring, flowing gas from the processing region through a plurality of holes formed in the ring to a pumping plenum and exhausting gas from the pumping plenum through an exhaust port disposed in the processing chamber.